Where should a backflow preventer be installed?

The backflow preventer is mandatory in Quebec in several situations according to the Plumbing Code and municipal regulations:

Where it's required:

• Building water entrance: a backflow preventer (DAr) must be installed at the building's water entrance and at every point where there is a risk of contamination; it must then be verified every year by a certified verifier (RBQ). It prevents contaminated water from the building from flowing back into the municipal network
• Excluded buildings: existing fully residential buildings of fewer than 9 dwellings or fewer than 3 storeys are excluded from these obligations (RBQ)
• Irrigation system: the connection must be designed and installed so as to prevent the entry of non-potable water, and the backflow preventer must be selected and installed in accordance with CSA B64.10 (Construction Code, Ch. III – Plumbing, art. 2.6.2.1, paras. 1 and 3). The device required therefore depends on the hazard level: the RBQ/CMMTQ guide on backflow preventers classifies irrigation without chemicals as moderate hazard and irrigation with chemicals as high hazard (Table II, pp. 34-35). Municipal by-laws may specify the device: for example, Quebec City's by-law requires « a dual check backflow preventer » on every automatic sprinkler system (R.R.V.Q. ch. E-1, art. 7, para. 2)
• Pool and spa: A backflow preventer is required on the water supply line
• Commercial buildings: Depending on the risk level (water treatment, laboratories, commercial kitchens)

Types of backflow preventers:

• Dual check valve: For standard residential use, about $30 to $50
• RPZ: For commercial/irrigation use, about $200 to $600

Annual verification and maintenance of a backflow preventer must be carried out by a certified backflow preventer verifier — a certificate issued under section 5 of the CSA B64.10.1 standard by an organization or association recognized by the AWWA — and it is the building owner who is legally required to have it done (Safety Code, Chapter I, Plumbing, article 7). Installing or modifying the device is plumbing work: it must be carried out by a company holding the RBQ 15.5 contractor licence and by workers holding a CCQ competency certificate.